I've just started using Mail.app, after switching from WinXP to OSX. Both Outlook and Mail.app have a preview pane, but in Outlook, I was able to configure it to only mark a message as unread after viewing the message for a given amount of time. As far as I can tell, Mail.app doesn't have this option - as I use the arrow keys to scroll through my inbox, every email is marked unread.
Is there a way to have Mail.app only mark a message as unread after, say, two seconds of viewing it? Are there plugins or anything for Mail.app?